1. Field of the Invention
The present invention relates to a pneumatic motor, and more particularly to a pneumatic motor for a pneumatic tool to have an enhanced structural strength.
2. Description of Related Art
A pneumatic motor is mounted in a pneumatic tool. When pressured air is led into the pneumatic motor, the pneumatic motor is rotated to drive a tool to rotate. With reference to FIGS. 9 to 11, a conventional pneumatic motor comprises a housing 50, an axle 60, and multiple blades 70. The housing 50 has an inlet 51 and an outlet 52. The inlet 51 is connected with a pressured air source. The axle 60 is rotatably mounted in the housing 50 and is eccentric to the housing 50. The axle 60 has multiple blade recesses 62 radially defined in the axle 60. The blades 70 are mounted respectively and movably in the blade recesses 62 of the axle 60. When pressured air is led into the housing 50 via the inlet 51, the blades 70 are pushed by the pressured air to rotate the axle 60 so as to output a driving force to a tool.
However, each blade 70 of the conventional pneumatic motor has a curved side edge 72, so the bottoms 622 of the blade recesses 62 are also curved for corresponding to the curved side edges 72 of the blades 70. Thus, the thickness of the axle 60 at a position being adjacent to an axis of the axle 60 is thin, but the portion being adjacent to the axis of the axle 60 has to bear a large load while the axle 60 is pushed to rotate by the pressured air. Therefore, the axle 60 is easily damaged, and the useful life of the pneumatic motor is reduced. Accordingly, the conventional pneumatic motor usually has six blades 70, such that the housing 50 is divided into six air chambers by the blades 70. However, each air chamber has a large volume, and the amount of the pressured air in each air chamber for pushing a corresponding blade 70 is large. Therefore, this will cause waste in use of the pressured air, and the torque provided by the pneumatic air is also limited.
In addition, to increase the number the air chamber and to reduce the volume of each air chamber by increasing the number the blades 70, which will causes the thickness of the axle 60 at a position being adjacent to the axis of the axle 60 become thinner. Thus, the structural strength of the axle 60 is reduced and cannot bear a large load, so the conventional pneumatic motor is easily damaged and the useful life of the conventional pneumatic motor is shortened.
To overcome the shortcomings, the present invention tends to provide a pneumatic motor to mitigate or obviate the aforementioned problems.